The disclosed subject matter allows test and measurement data to be generated from a geo-location overlay network in a host wireless communication system.
The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile appliances” or “mobiles”, has become prevalent in today's society. Recently, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position, or “geo-locate” a mobile appliance in certain circumstances. For example, the Federal Communication Commission (FCC) has issued a geo-location mandate for providers of wireless telephone communication services that puts in place a schedule and an accuracy standard under which the providers of wireless communications must implement geo-location technology for wireless telephones when used to make a 911 emergency telephone call (FCC 94-102 E911).
In addition to E911 emergency related issues, wireless telecommunications providers are developing location-enabled services for their subscribers including roadside assistance, turn-by-turn driving directions, concierge services, location-specific billing rates and location-specific advertising.
To support FCC E911 rules to locate wireless 911 callers, as well as the location enabled services, the providers of wireless communication services are installing mobile appliance location capabilities into their networks. In operation, these network overlay location systems take measurements on RF (Radio Frequency) transmissions from mobile appliances at base station locations surrounding the mobile appliance, and estimate the location of the mobile appliance with respect to the base stations. Because the geographic location of the base stations is known, the determination of the location of the mobile appliance with respect to the base station permits the geographic location of the mobile appliance to be determined. The RF measurements of the transmitted signal at the base stations may include, but are not limited to, the time of arrival, the angle of arrival, the signal power, or the unique/repeatable radio propagation path (radio fingerprinting) derivable features. In addition, the geo-location systems can also use collateral information, e.g., information other than that derived for the RF measurement to assist in the geo-location of the mobile appliance, for example, location of roads, dead-reckoning, topography, map matching, etc.
In a network-based geo-location system, the mobile appliance to be located is typically identified and radio channel assignments determined by (a) monitoring the control information transmitted on a radio channel or wireline interface that is part of the wireless communication system for telephone calls being placed by the mobile appliance to detect calls of interest, e.g., 911 calls, (b) a location request provided by a non-mobile appliance source, e.g., an enhanced services provider. Once a mobile appliance to be located has been identified and radio channel assignments determined, the location determining system is first tasked to determine the geo-location of the mobile appliance, and then directed to report the determined position to requesting entity or enhanced services provider.
The monitoring of the RF transmissions from the mobile appliance or wireline interfaces containing call setup or channel assignment information to identify calls of interest is known as “tipping”, and generally involves recognizing a call of interest being made from a mobile appliance and collecting the call setup information. Once the mobile appliance is identified and the call setup information is collected, the location determining system can be tasked to geo-locate the mobile appliance.
FIG. 1 shows a conventional mobile-appliance communication system having a mobile switching center 45 connected by wire lines 41 to base stations 10a–c for communicating with a mobile appliance 20. Each base station 10 generally comprises signal processing equipment and an antenna for transmitting to and receiving signals from the mobile appliance 20 as well as communicating with other base stations and one or more centrally located control and processing stations (not shown). A mobile appliance location determining sensor 30a–c (i.e., geo-location sensor, or wireless location sensor “WLS”, etc.) may be positioned at some or all of the base stations 10 to determine the location of a mobile appliance 20 within the signal coverage area of the communication system.
A network overlay geo-location system is generally composed of two main components, one that resides at the base station that makes measurements on the RF signal emanating from the wireless device, the wireless location sensor (WLS) 30 and one that resides at the mobile switch that tasks the geo-location sensor groups to collect data and then uses the data to compute a location estimate, this latter component is generally referred to as the Geo-location Control System (GCS) 50 and is connected to the mobile positioning center MPC 40.
FIG. 2 is a flow chart illustration a typical geo-location process 200. In the normal course of operation, the GCS may be tasked by an outside entity to generate a location estimate on a particular mobile appliance in block 210. The tasking typically is accompanied by information on the mobile of interest which may include the serving base station and sector for the call and the RF channel (frequency, time slot, CDMA code, etc.) being used by the wireless communications network to complete the wireless connection. Once the GCS receives this tasking, based on the serving sector, it tasks a set of WLS units proximate to the serving sector or serving base station to detect the signal from the target mobile appliance in block 220. The set of WLSs make measurement on the RF emission of the mobile appliance's signal, as indicated by block 230. The WLS units then report the measurements to the GCS. The GCS then computes a location estimate typically using some mathematical or data matching algorithm, as represented in block 240, and reports the estimated location to the requesting entity, as indicated in block 250. In an alternative embodiment, control channels/information on either RF or wireline links used to set up calls in the wireless network can be scanned to detect the placement of a call of interest. The signaling that occurs on the control channel can be used to determine location, or RF traffic channel parameters can be extracted from the control channel messaging to determine which traffic channel to use for location related measurements.
Network overly location systems typically locate a mobile appliance on the traffic channels of a wireless network. The systems typically use sensors employing techniques of time difference of Arrival (IDOA) supplemented with Angle of Arrival (AOA) in some cases to perform a multi-site location computation. The traffic channel information is provided through a separate process, with one option being a wire line interface (FIG. 1) providing MOBINFO (IS-41 Mobile Information) parameters passed by the Mobile Positioning Center 40 (MPC) (FIG. 1) as part of the GPOSREQ (J-STD-036 Geo-location Position Request) message
Operators of commercial wireless communication networks, as do most network operators, need to determine the performance of their wireless networks to effect repairs, plan expansion and adjudicate customer complaints. The current state of the art for collection of this data is to perform drive testing with a specialized drive test unit comprised of a test mobile telephone, GPS receiver, and data storage capability such as a laptop computer. Calls are placed from the test mobile and data is collected from an interface port on the phone. The collected data is composed of information related to the operation of the phone in the wireless network and typically includes received and transmitted power levels, handover status, data transmission quality (e.g., bit error rates, frame error rates), etc., along with location and time stamping. The drive test process produces data on the operation of the test mobile only and signals received at the test mobile. Thus, the performance of the reverse link and its associated merit parameters are not captured. Additionally, a technician is required to perform the drive testing. The prior art method also introduces dedicated calling traffic to the network and results in an additional associated system load. Yet other prior art used data collected at the Mobile Switch for these purposes. This method is generally of poor value given the collected measurements cannot be referenced to a mobile phone actual location, and only to a serving sector (this is the granularity with which the mobile switch knows the location of a mobile).
Geo-location systems, like the one illustrated in FIGS. 1 and 2, when not being tasked to locate a mobile appliance for emergency or other location-based services, are effectively in an idle mode. The tasking duty cycle can vary depending on what uses are being made of the location data For E911 purposes, the effective utilization of the location network is low. With other location enabled value added services, the use may be higher, depending on the service. A service providing turn by turn instructions to a motorist would likely be higher than a service that provides road side assistance.
The disclosed subject matter utilizes this excess capacity of the location network to generate test and measurement data. An additional embodiment gathers test and measurement data on the actual E911 calls, or on any calls being located for other value added services.
Thus is it an object of the disclosed subject matter to obviate the deficiencies of the prior art and provide in a geo-location system the ability to collect test and measurement data normally associated with drive testing methodology automatically and with no manual labor component, without adding any dedicated calling traffic to the network. The disclosed method and apparatus also enables the ability to collect both forward and reverse link data for a given wireless connection with installation of equipment at reverse link sites only. Another benefit of the disclosed subject matter is the ability to operate a continuous background task for network overlay location which does not burden the network.
These objects and other advantages of the disclosed subject matter will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal or the claims, the appended drawings, and the following detailed description of the preferred embodiments.
Common elements are identified with similar reference number where advantageous.